Breaking capacity and thermal derating — what the ratings mean for panel fit
The 3VA1125-6EF32-0JC0 is a Siemens SENTRON 3-pole molded case circuit breaker (MCCB) designed for line protection. Its headline breaking capacity is 220 kA at 240 V, stepping down to 154 kA at 415 V, 121 kA at 440 V, and 17 kA at both 500 V and 690 V — so the available fault current at the installation point must be checked against the voltage-specific rating, not the highest number. The continuous current rating is 25 A from 40 °C through 50 °C, then derates to 24 A at 55–60 °C, and 23 A at 65–70 °C; a panel builder should size the branch circuit for the actual ambient temperature inside the enclosure, not the nominal 25 A.
Integrated accessories and mounting footprint
This MCCB ships with a shunt trip (STL) release and two HQ-rated auxiliary switches factory-fitted — no field-assembly of those accessories. The supplied basic switch is order code 3VA11256EF320AA0. Dimensions are 70 mm depth, 76.2 mm width, 130 mm height, which fits the standard SENTRON 3VA panel footprint. Rated insulation voltage is 800 V. Maximum power loss is 8.5 W, a figure to include in enclosure thermal calculations.